1. Field of the Invention
This invention relates in general to an automated material handling process in production lines and an automated material storage and retrieval system for production line. In particular, this invention relates to an automated storage and retrieval means for use in the manufacturing facilities that require small quantities of large number categories of materials and/or components with optimized efficiency and inventory status.
2. Technical Background
Material mis-management in production operations in the computer and communication hardware manufacturing companies is frequently the major cause for severe financial damages in this high-tech industry. The computer and communication hardware manufacturing industry is characterized by several phenomenon that are distinguished from other manufacturing industries.
First of all, the computer and communication hardware manufacturing business is well known for its vast variety of product items. In managing raw materials for a vast variety of products, complication in material categories and flow control complicate the management problem. Then, there is the typical fast delivery requirement placed by customers. As most of the computer and communication hardware product manufacturers always face severe competition, lead time for product orders becomes an important factor in the competition. Basically, rapid delivery after confirmed order is necessary. Otherwise, the customer turns to other suppliers, and therefore slow delivery means higher possibility of losing business opportunities.
The computer and communication hardware product manufacturing industry is also characterized by the short product life cycles. Typical product life cycles are frequently less than one year. Product designs must be improved constantly to meet user demands. Once a particular product is upgraded, some of its original components become obsolete, at least in the later version of the product. If the surplus components or materials can not find their use in other products as soon as possible, then they become waste inventory.
Further, materials used for the production of computer and communication hardware are frequently small in their physical sizes yet have relatively high unit prices. They tend to be lost in the storage warehouse or warehousing area if the inventory data is not properly controlled. Once forgotten and lost in the warehouse, these components become obsolete even if they were recovered after a period of time. The typical high unit prices amplify the lost in material costs for the manufacturer.
Note that computer and/or communication product manufacture requires the use of various types of materials or components. In many occasions, a raw material used for the manufacture is itself a component made up of its own raw materials. For convenience, the term material will be used to generally designate either the materials or the components used for such manufacturing activities. Meanwhile, the term warehouse will be used in the following text to designate the storage space used for stocking the production materials, either it is a physically isolated room or house for such purpose, or a simple designated warehousing area.
Thus, due to the above-distinguished characteristics, material management in computer and communication hardware product manufacturers becomes severely important for the profit ability. For example, insufficient material reserve delays delivery of product, and sometimes even leads to complete lost of business. Excessive material supply leads to dead material inventory that stagnates capital flow, and even eats up capital if the surplus of material was not properly consumed rapidly in other product lines.
In order to cope with these material management problems for computer and communication hardware product manufacturing business, vendors have started to employ material requirement planning (MRP) procedures that are based on factory control systems including master production schedule (MPS), bill of material (BOM) control, as well as inventory information. Calculations are made to determine items, quantities and time schedule for the required materials.
However, many of the warehouses used for the raw material storage are still operating in the conventional manner. In these warehouses, materials are stored in shelves, and sometimes some of the materials are temporarily placed alongside the production lines, it is quite difficult to maintain realtime inventory control via inventory counting. Unrealistic inventory records therefore leads to low-efficiency material control for these storage facilities.
To solve the inventory control problems as outlined above for the computer and communication hardware product manufacturers, automated and highly-efficient warehousing system must be developed. These automated warehousing systems must be able to allow for rapid access to the stored inventory, maintain realistic record of the quantities and positions of all the stored materials, and capable of linking with the MRP system.
The concept of automated storage and retrieval means (ASRS) is one such warehousing system that has been developed to meet such needs. Though ASRS has been around for a period of time, however, it was designed for the material storage and retrieval emphasizing the control of large quantities of small categories of materials. This essentially contradicts the requirement of computer and communication hardware product manufacturers that needs to handle relatively large categories of small quantities of materials.
For the purpose of description of the invention, more details of the conventional ASRS are examined herein. Based on the physical units of material storage and retrieval, the conventional ASRS can be summarized in Table 1 below.
TABLE 1 ______________________________________ Retrieval Method Storage Unit Retrieval Unit ______________________________________ 1 Pallet Pallet 2 Pallet Case 3 Carton Carton 4 Carton Case 5 Case Case 6 Case Piece 7 Piece Piece ______________________________________
In the table above, carton is defined to be a larger box that contains a number of cases of material. Some materials are too small that should be stored in cases containing a multiple number of them.
Based on weighting at storage and retrieval, operation of the conventional ASRS can be categorized between the heavy- and light-weight handling systems. Light-weight handling ASRS. Light-weight ASRS handling systems employ the scheme of the fifth item in Table 1 above. A comparison of methods 1, 3 and 5 in the Table shows that the units of storage and retrieval are the same, either pallet, carton or case. Conventional ASRS are suitable for the storage and retrieval of the same units, preferably physically large units such as pallets or cartons. This, in particular, is very suitable for warehouses of large companies. For typical computer and communication hardware product manufacturers, methods 6 and 7 are preferable. Inventory items are stored in units of case and retrieved in single items. Sometimes single items are stored and retrieved as well. Thus, such are procedures for ASRS not suitable for computer and communication hardware product manufacturers.
In general, the operation of material delivery to the production lines in the computer and communication hardware product manufacturing facilities are not rigorous enough, frequently with large amounts and categories of materials stacked alongside the production lines. Some of these materials may be needed immediately, while others may not. Thus, the conventional material delivery operation in computer and communication hardware product manufacturing facilities are characterized by at least the following drawbacks.
First of all, retrieval of a material in this manner is prone to mistakes. Since all the materials are stacked alongside the production line, it is not only more difficult to locate the right inventory in the stacked piles, but also there is the high possibility of fetching the wrong material.
Secondly, the stacked piles of materials in the proximity of the production lines constitute possible obstacles for the access to the production line by both the line operators and the necessary equipments.
Next, there is the high possibility that valuable materials might be lost either intentionally or unintentionally. A possible scenario is that some high-cost microprocessor or memory IC are found lost only after a batch of product is processed. Even so, it is difficult to try to trace the whereabout of the missing materials and how they were missing since it has been a period of time from the incidence.
Then, there is the problem of incorrect and unrealistic inventory record. Most of the materials used for the production operations are stockpiled along side the production line. Since the piling is most certainly in the manner arranged for the convenience of the retrieval from the line, not for the management of the materials themselves, therefore, it is frequently the situation that the corresponding records supposed to reflect the status of the categories, quantity and even locations of the materials are not correct. This raises problems for the inventory control. Bad inventory control in turn leads to poor material demand planning, and as a result, overall manufacturing efficiency deteriorates.
Thus, computer and communication hardware product manufacturing is frequently characterized by the requirement of small quantities of large model numbers of products. Sometimes batches of about several thousands or even hundreds of pieces of a particular product model is required to be manufactured. For a manufacturer to handle these small batches of various product models efficiently (i.e., in a profitable manner), inventory control must be precise. Material reserve in stock must be calculated in the daily basis, sufficient only for the latest order of production. Since, as mentioned, these materials are usually small in physical sizes, each occupying only a small warehousing space in the ASRS, it is therefore impractical to use separate cases for each piece of the material. If too few material pieces are stored in one unit of case in the ASRS, excessive storage and retrieval accesses performed by the elevated and railed mechanical access mechanism would not only produce delays in the fetching of raw material to the production lines but would also wear out the mechanism prematurely. In worst cases, the entire mechanism might even be paralyzed.